What type of bond and type of overlapping are present in the $N_2$ molecule?

Which of the following combinations does not form a $\sigma$ bond?
$(i) \ 2p_y - 2p_y$
$(ii) \ 2p_z - 2p_z$
$(iii) \ 2s - 2p_x$
$(iv) \ 2p_x - 2p_x$

In a $\sigma$ bond,

Given below are two statements :
Statement $(I)$ : The oxidation state of an element in a particular compound is the charge acquired by its atom on the basis of electron gain enthalpy consideration from other atoms in the molecule.
Statement $(II)$ : $p\pi-p\pi$ bond formation is more prevalent in second period elements over other periods.
In the light of the above statements,choose the most appropriate answer from the options given below :

Select the $CORRECT$ statement if the internuclear axis is the $y-$ axis.

What is the total number of $\pi$ bonds in the compound $CH_2=CH-CH=CH-COOH$?